The present invention relates to splicing signal paths and power-supplying feeders of an optical submarine cable and an optical submerged repeater in an optical submarine cable system which employs, as a transmission medium, an optical fiber formed principally of quartz.
A signal path in the optical submarine cable system is constituted by an optical fiber, which is formed principally of quartz and hence is fragile and readily broken. In addition, its mechanical strength is apt to be degraded under circumstances of much moisture. Therefore, in a case the optical fiber issued as a submarine cable, it is of importance to protect the optical fiber from the seawater pressure and to hold back the seawater; such steps are taken for the optical submarine cable.
In the interconnecting of such tail cables, each having the optical fiber and the power-supplying feeder formed as a unitary structure, it is extremely difficult to install an extra length of optical fiber in a state of safety unless it is very short. For optical fiber splicing are employed connector splicing, V-groove butt splicing and fusion splicing methods but, in an optical submarine cable system, fusion splicing is the most excellent in terms of splice loss and longterm reliability. In a case of use of a fusion splicing method, it is necessary that a plurality of single-mode optical fibers be spliced together for use in the optical submarine cable be given an extra length of 30 cm or so at maximum even if the splicing skill level of the fabricator is taken into account. The reason for this is that in the case of the single-mode optical fiber, if satisfactory optical and mechanical characteristics cannot be obtained by one splicing operation, the optical fiber is made shorter by a repetition of the splicing operations. It is expected that dispersion in the length of the fibers after splicing will be reduced by improvements in a splicing jig and devices in the future, but it is necessary to consider that some dispersion will be left unless the entire splicing operation is fully automated. Further, the optical fiber spliced portion is mechanically weak, and hence it must be protected from an external force and it is necessary to secure the long-term reliability of the spliced portion even after it is installed in an extra-length housing portion. Moreover, considering works on the cable ship, it is desirable that the spliced portion housing structure and assembling structure be simple as much as possible.